NEWTOWN, Conn. (CBSNewYork/AP) – Officials said Sunday that with the amount of ammunition Newtown elementary school massacre gunman Adam Lanza was carrying, he could have killed every student at the school.

She was an avid gun collector, shot four times in the head here before her son took her weapons and unleashed his horror at Sandy Hook Elementary School. His firepower included enough rounds of ammunition to kill all the students, and police believe he likely had bigger, even more gruesome plans.

“There was a lot of ammo, a lot of clips,” said Connecticut State Police Lt. Paul Vance. “Certainly, a lot of lives were potentially saved.”

Connecticut State Police Lt. Paul Vance confirmed Sunday afternoon that Lanza had multiple high-capacity magazines for the rifle. He said it was too early to figure out how many shots had been fired, but he estimated the number in the hundreds.

Multiple shell casings and rounds were found at the scene, Vance said.

Law enforcement officials said Lanza used the .223 semiautomatic rifle to kill all the children and adults, and one of the two handguns he was carrying to kill himself. The third gun he carried into the school, another semi-automatic pistol, was still in his military-style cargo pants when his body was discovered, authorities said.

Officials also said given the presence of a fourth weapon in the trunk of his mother’s black Honda, Lanza was likely thinking of some kind of broader attack.

Residents were stunned that Lanza still had multiple clips, each with 30 bullets per capsule.

“I feel that we need to look at some of the laws and make adjustments,” said Diane Wilson.

Also Sunday, Gov. Dannel Malloy’s statement Sunday that the shooter decided to kill himself only when he heard first responders closing in after about 10 minutes of shootings.

Investigators checked out leads in dozens of gun stores and shooting ranges across Connecticut. Some officers were sidetracked responding to a phoned-in threat at St. Rose of Lima Church, and worshippers were evacuated mid mass.

Police searched and found nothing dangerous.

On Sunday night, some of focus continued to be on Lanza’s mother’s home, where inside the immaculately clean surroundings two computers were found smashed to pieces.

Meanwhile, as police combed through the gruesome and complex crime scene, the picture of what happened Friday at Sandy Hook Elementary School began to shift slightly.

It appears Lanza forced his way into the school using one of his weapons, CBS 2’s Lou Young reported.

“I can tell you it’s believed he was not voluntarily let into the school at all, that he forced his way into the school,” Vance said.

Police have identified the individual bodies and report the 20 murdered children were all age 6 or 7 and each were shot multiple times.

“I only did seven of the autopsies. The victims I had ranged from three to 11 wounds apiece, and I only saw two of them with close range wounds,” chief medical examiner Dr. H. Wayne Carver told CBS 2’s Lou Young.

A law enforcement source told CBS News that investigators are having difficulty in determining exact number of rounds shot by Lanza because in some cases, the same one bullet hit more than one child.

The source said that in one of the classrooms, some children were found clustered together in one spot along with their teacher, perhaps trying to hide from the gunman. The source said the teacher appeared to be shielding the kids. All were found dead.

As for the motive, police are discounting any altercation. The presumed killer’s aunt suggested his murdered mother had difficulties both with Adam Lanza and the school system because of her son’s personality issues.

“I know she’d had issues with school. She eventually wound up home-schooling him because she battled with the school district, in what capacity I’m not 100 percent certain. If it was behavior, it was learning disabilities, I really don’t know, but he was a very, very bright boy. He was smart,” Marsha Lanza told Young.

Adam Lanza’s mother Nancy was not a teacher at the school as originally reported.

Two law enforcement sources told CBS News that Adam Lanza did attend Sandy Hook school at one time, but it remains unclear as to when and for how long.

A source briefed on the investigation told CBS News that Nancy Lanza was said to be demanding on her children. Even though Adam was highly intelligent she held him to high standards and even pressed her sons to measure up at the shooting range where she taught them to shoot, the source said.

Her sister-in-law said it was no surprise there were multiple weapons in the house.

“Last time we visited with her in person, yeah, we talked about prepping and ‘are you ready for what can happen down the line when the economy collapses?'” Marsha Lanza told CBS 2’s Young. “I didn’t actually see them, we just talked. I knew she had three.”

Meanwhile, officials were working to determine who bought and registered the guns and when. Initial reports said they were registered to Lanza’s mother.

Malloy offered no possible motive for the shooting and a law enforcement official has said police have found no letters or diaries left behind that could shed light on it.

All six adults killed at the school were women. Of the 20 children, eight were boys and 12 were girls.

Asked whether the children suffered, Carver said, “If so, not for very long.” Asked how many bullets were fired, Carver said, “I’m lucky if I can tell you how many I found.”

Parents identified the children through photos to spare them some shock, Carver said.

State police cautioned that there are imposters out there disseminating false information about the investigation.

“Social media websites that contain information related to this case are not being posted by the Connecticut State Police, are not being posted by the Newtown police,” Vance said.

There are even posts claiming to be from the gunman, Vance said. Those posted are being investigated for prosecution, Vance added.

Vance said anyone who abused social media in connection with the case will be prosecuted to the fullest extent of the law.

Vance also said police would not be releasing details about the timeline of the shooting for some time as the investigation continues.

The rifle used was a Bushmaster .223-caliber, according to an official with knowledge of the investigation who was not authorized to speak about it and talked on condition of anonymity. The gun is commonly seen at competitions and was the type used in the 2002 sniper killings in the Washington, D.C., area. Also found in the school were two handguns, a Glock 10 mm and a Sig Sauer 9 mm.

A law enforcement official said Saturday that authorities were investigating fresh leads that could reveal more about the lead-up to the shooting. The official spoke on condition of anonymity because he was not authorized to discuss the matter publicly.

Ginger Colbrun, spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said earlier there was no evidence Lanza was involved in gun clubs or had trained for the shooting. When reached later in the day and asked whether that was still true, she said, “We’re following any and all leads related to this individual and firearms.”

Dean Price, director of the Wooster Mountain State Range – a shooting range in Danbury – said two ATF agents visited the range Friday night and stayed into the early morning looking through thousands of names on sign-in logs.

He said that he had never seen Adam or Nancy Lanza there and that agents told him they did not find their names on the sign-in sheets.

Law enforcement officials have said they have found no note or manifesto from Lanza of the sort they have come to expect after murderous rampages such as the Virginia Tech bloodbath in 2007 that left 33 people dead.

Education officials said they had found no link between Lanza’s mother and the school, contrary to news reports that said she was a teacher there. Investigators said they believe Adam Lanza attended Sandy Hook many years ago, but they had no explanation for why he went there Friday.

Authorities said Adam Lanza had no criminal history, and it was not clear whether he had a job. Lanza was believed to have suffered from a personality disorder, said a law enforcement official who spoke on condition of anonymity.

Another law enforcement official, also speaking on condition of anonymity, said Lanza had been diagnosed with Asperger’s, a mild form of autism often characterized by social awkwardness.

People with the disorder are often highly intelligent. While they can become frustrated more easily, there is no evidence of a link between Asperger’s and violent behavior, experts say.

The law enforcement officials insisted on anonymity because they were not authorized to discuss the unfolding investigation.

Richard Novia, the school district’s head of security until 2008, who also served as adviser for the school technology club, of which Lanza was a member, said he clearly “had some disabilities.”

“If that boy would’ve burned himself, he would not have known it or felt it physically,” Novia said in a phone interview. “It was my job to pay close attention to that.”

Amid the confusion and sorrow, stories of heroism emerged, including an account of Hochsprung, 47, and the school psychologist, Mary Sherlach, 56, rushing toward Lanza in an attempt to stop him. Both died.

“I think a lot of people would like to get back to whatever normal will look like as quickly as possible,” Malloy said on CBS News’ “Face The Nation” on Sunday morning.

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